A wide variety of systems are known for producing fluids of economic interest from subterranean geological formations. In formations providing sufficient pressure to force the fluids to the earth's surface, the fluids may be collected and processed without the use of artificial lifting systems. However, where well pressures are insufficient to raise fluids to the collection point, artificial means are typically employed, such as pumping systems. These pumping systems might be located downhole or subsea.
The particular configurations of an artificial lift pumping systems may vary widely depending upon the well or subsea conditions, the geological formations present, and/or the desired completion approach. In general, though, such systems typically include an electric motor driven by power supplied from the earth's surface. The motor is coupled to a pump (or a compressor), which draws wellbore fluids from a production horizon or from subsea ground and imparts sufficient head to force the fluids to the collection point. Such systems may include additional components especially adapted for the particular wellbore fluids or mix of fluids, including gas/oil separators, oil/water separators, water injection pumps, and so forth.
The operation of these pumps (and/or compressors) can be impaired if/when impurities (e.g. sand particles) and/or ingression of water and/or seawater appears in the barrier fluid. Under such circumstances, the barrier fluid/oil degradation can cause increased pump (and/or compressor) wear and/or motor insulation problems, and can lead to increased equipment downtime.
Within known systems, the subsea pumps/compressors are connected to the surface via an umbilical from a topside production unit. The barrier fluid can be cleaned by filtering/water separation systems, monitored and checked before it is pumped from a Hydraulic Pressure Unit (HPU) through the umbilical and into the pump/compressor module.
However, the barrier fluid can be contaminated after being pumped from the HPU. For example, loose particles may be present in the umbilical that cannot be suitably cleaned; particles can be generated from various sources such as worn umbilical tubing; water/seawater ingression can occur at various locations within the system; particles such as dust and/or lacquer can enter the electric motor; particles can be loosened from the inside surface of the electric motor stator, rotor or cable terminations; and particles can be generated from rotodynamic wear.
Barrier fluid contamination can lead to problems in the motor insulation and negatively affect the overall performance of the barrier fluid in the pump and/or compressor. For example, water ingress can degrade properties of the barrier fluid such as in load carrying ability, corrosion protection ability, and lubrication ability. Particles in the barrier fluid can wear the internal surfaces causing more particles, which can accelerates the wear process of bearings, circulation impeller, coupling and dynamic seals.